Went to take my wife's friends for a boat ride last Friday. Backed off the dock and part way out of the harbor and put it in forward and nothing. Fortunately the harbor was empty and it was calm out. The drive has been working perfectly and I just had it out the week before with no issues. I was able to back into a slip and raised the hatch and pulled the shift cable off tried it by hand and no forward. I was able to back up to the ramp and get the boat turned around to get it back on the trailer. I checked the top plug for metal and the oil for brass and nothing. So I pulled the drive and shifted it manually to see if it was the drive, pushed the lever in and it went into forward perfectly. Put everything back together and double checked the cable adjustment with the Merc tool and with everything adjusted as recommended it would not go into forward. Is it possible that the cable is buckling somewhere and not pushing the drive into forward?

cable is broken it sounds like some where in the sleeve. regards Dan

The clutch on the inner drive shaft is the issue. If you give it more throttle in FWD, all at once it will go in gear with a joilt

The temp fix is pull the clutch, out and polish the shaft and gear. It will work for a while longer.

The full fix, replace the drive shaft, clutch and gear set

https://www.mercruiserparts.com/bam/.../30968/5398/90

I tried revvving the motor while in forward and no response. I was also able to shift into forward with the drive off with no delay. I am going to order a new cable and just pull the core and see if that fixes the problem. Just odd how one day it's working perfect instant response and next day nothing. Odd part is that to go into forward the cable is pushing the shift lever, that's why I thought the cable is buckling. The shift cable was replaced with the newer version about 8 years ago.

In that case it might be the cable from the throttle, the cab;e is pulled in FWD so drive cable is pushed. Even with that it wouldn't explain for it comes out of REV and back into neutral

I pulled the drive cable off of the shift mechanism and tried it directly and still no forward. I can't tell if something is worn in the drive and the cable just isn't going far enough or if the cable isn't pushing it properly.

When you pull the drive off isn’t there a nut on the end of the shift cable that holds it in the transom? Did that come loose allowing cable to push away and only work in one direction?
Could the cone clutch be slipping under load but when you checked it by hand you just couldn’t put enough load on it?(prob not)

You may be right, that's very plausible. I ordered a new cable either way and I will replace it this weekend and check to see that the outer portion is tight at the drive.

I'm having the same exact problem, pulled the drive and found the inner shift fork not raising enough to engage clutch. If I move it up 1/16 it engages. I'll be ordering a new shift plate and yoke tomorrow.

Found the problem. Shift cable was rubbing on the coupler. Put a new cable in and I'm back on the water.